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 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Introduction\n",
    "\n",
    "The notebook comes alive with the interactive widgets"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Speeding up the bottleneck in the REPL\n",
    "\n",
    "<img src=\"Flow.svg\"></img>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "9*9"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def f(x):\n",
    "    print(x * x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "f(9)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "from ipywidgets import *"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "interact(f, x=(0, 100));"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Interactive Jupyter widgets\n",
    "\n",
    "A Python widget is an object that represents a control on the front end, like a slider. A single control can be displayed multiple times - they all represent the same python object."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "slider = FloatSlider(\n",
    "    value=7.5,\n",
    "    min=5.0,\n",
    "    max=10.0,\n",
    "    step=0.1,\n",
    "    description='Input:',\n",
    ")\n",
    "\n",
    "slider"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "slider"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The control attributes, like its value, are automatically synced between the frontend and the kernel."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "slider.value"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "slider.value = 8"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can trigger actions in the kernel when a control value changes by \"observing\" the value. Here we set a global variable when the slider value changes."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true,
    "scrolled": true
   },
   "outputs": [],
   "source": [
    "square = slider.value * slider.value\n",
    "def handle_change(change):\n",
    "    global square\n",
    "    square = change.new * change.new\n",
    "slider.observe(handle_change, 'value')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "square"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can link control attributes and lay them out together."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "text = FloatText(description='Value')\n",
    "link((slider, 'value'), (text, 'value'))\n",
    "VBox([slider, text])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Jupyter widgets as a framework\n",
    "\n",
    "Jupyter widgets forms a framework for representing python objects interactively. Some large open-source interactive controls based on Jupyter widgets include:\n",
    "\n",
    " - bqplot - 2d plotting library\n",
    " - pythreejs - low-level 3d graphics library\n",
    " - ipyvolume - high-level 3d graphics library\n",
    " - ipyleaflet - maps"
   ]
  }
 ],
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